#include<bits/stdc++.h>
using namespace std;
int a[10001]={1};
int main()
{
	int n;
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		if(i%2==0)
			a[i]=a[i-1]+i/2;
		else
			a[i]=a[i-1]+i/2+1;
	}
	cout<<a[n];
    return 0;
}
